Question

Define valency and variable valency with examples.

Answer 1

Valency:

• The combining capacity of the atom of an element is called its valency.
• It is always a whole number.
• Valency varies from 1 to 8.
• Valency is always positive.
• An element with a valency is one called monovalent, with two called divalent.
• The valency of noble gases is zero.

Variable valency:

• Some elements show more than one type of valency, these types of valency are called variable valency.
• Some elements like lead, tin, copper, mercury, iron, etc exhibit variable valency.
• Elements with variable valency are as follows:

Copper (Cu) = Cuprous (Cu²⁺) and cupric (Cu³⁺)

Iron (Fe) = Ferrous (Fe²⁺) and Ferric (Fe³⁺)

Mercury(Hg) = Mercurous (Hg ⁺¹) and mercuric (Hg ⁺²)

Silver (Ag) = Argentous (Ag⁺¹) and argentic (Ag⁺².)

Tin (Sn) = Stannous (Sn⁺²) and Stannic (Sn⁺³)